"I spent a lot of time listening to his voice, mostly his private phone callsâ€¦ You have to find things that no one has found in the voice," he said of the process he went through to portray Kennedy.

"It's a little bit like watching Titanic. You know how it ends, and yet you cannot believe it's going to end the way it ends. You're on the edge of your seat. The other thing that moved me is what a love story it is."